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[quote user="Phoebe Vet"] You are in error. You are correct about almost the entire force of impact being transferred to the car, but that is not the case with 100% of the debris. There will be debris and marks at the point of impact. In this picture, notice that the train is a small dot in the background, an indicator of how hard it hit the truck.The tractor of the truck is down there with the train.  Then notice that there is a substantial amount of debris on the ground over the entire crossing.  What remains of the trailer is on the far side of the crossing, but the debris field starts at the point of impact. <IMG alt="" src="http://i248.photobucket.com/albums/gg164/phoebevet/Piedmont%20Accident/144-AMTRAK_5_standalone_prod_affili.jpg" border=0>    There is a significant quantity of "stuff" clinging to the underside of a vehicle.  It will be knocked off if the vehicle is suddenly accelerated by an impact and will fall pretty much straight down. [/quote] I see your point, but I am not sure that the collision you show is completely analogous to the Anoka crash.  You show a semi trailer full of say 20 tons of relatively dense, tightly stacked, loose objects.    <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p> Because the trailer is perhaps 30 feet long, and the locomotive is only 10 feet wide, wherever the locomotive strikes the trailer, the majority of the trailer and its load will be not be in line with the impact.  The acceleration of that part of the load that is not in line with the impact depends on the ability of the trailer to transmit the acceleration force to it from the part of the trailer that is in line with the impact.  The trailer does not have that degree of structural strength, so it torn in two as the locomotive carries the part it strikes forward, and leaves the rest behind.   <o:p></o:p> To look at it another way, say you have a stick of soft butter as high and wide as a semi trailer and 500 feet long, stalled on the track, and the train hits it dead center.  Most of that butter on either side of the impact is not going to even move, so you could say that it is a part of a debris field that begins right at the point of impact. <o:p></o:p> I think you tend to get a different result when a train hits a car perfectly broadside and none of the car extends beyond the locomotive on either side.  Even if debris is immediately detached, it is still in line with the locomotive, and being pushed forward by it.    Furthermore, I suspect that ability to withstand disintegration is greater (proportionately) with a car loaded with human occupants versus a semi trailer loaded with many tons of stacked, loose objects.  If you had a semi trailer full of BBs for instance, I suspect that shock of impact would act like an explosion and throw BBs in all directions, so some of them might land in locations prior to the point of impact with respect to the train travel direction.   Certainly the Anoka crash left a debris field.  Apparently it was something like 200 feet long, and it did begin on the crossing in the proper lane for the vehicle.  The only question is:  Was the vehicle actually struck in that lane or was it struck in the preceding lane.  There is only 15 feet of difference between them.
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